DllImport can import C++ functions from DLL Libraries.

using System.Runtime.InteropServices;
[DllImport("winInet.dll")]
private static extern bool InternetGetConnectedState(ref int dwFlag, int dwReserved);
private const int INTERNET_MODEM = 1;
private const int INTERNET_LAN = 2;
public void InetConnectStat()
{
System.Int32 dwFlag = new int();
if (!InternetGetConnectedState(ref dwFlag, 0))
{
Console.WriteLine("Error, Internet Not Connected!");
}
else
{
if ((dwFlag & INTERNET_MODEM) != 0)
Console.WriteLine("Internet speed maybe slow.");
else
{
if ((dwFlag & INTERNET_LAN) != 0)
Console.WriteLine("Internet Connected!");
}
}
}